now the error creeps in. i am able to decompress the file i.e in /home/trial/x.tar is formed but when i try to untar it the result in shown in the webpage(running the php script) instead of untaring it in the /home/trial folder).

right. if you try something simple, like create a directory in the root, set it with 777 permissions, and under php do something like:
exec("echo helloworld > /testdir/test.txt");

does that work? it all sounds like a matter of permissions of the user php is running under to me

no it doesn't work.no file is created. But if i create a file test.txt and set the permissions of this file to 0777 then run the php script , later when i open the file it shows that the file is of one line but nothing is written

Configuration
PHP Core
Directive Local Value Master Value
allow_call_time_pass_reference On On
allow_url_fopen On On
always_populate_raw_post_data Off Off
arg_separator.input & &
arg_separator.output & &
asp_tags Off Off
auto_append_file no value no value
auto_prepend_file no value no value
browscap no value no value
default_charset no value no value
default_mimetype text/html text/html
define_syslog_variables Off Off
disable_classes no value no value
disable_functions no value no value
display_errors On On
display_startup_errors Off Off
doc_root no value no value
docref_ext no value no value
docref_root no value no value
enable_dl On On
error_append_string no value no value
error_log no value no value
error_prepend_string no value no value
error_reporting no value no value
expose_php On On
extension_dir /usr/local/apache/lib/php/extensions/no-debug-non-zts-20020429 /usr/local/apache/lib/php/extensions/no-debug-non-zts-20020429
file_uploads On On
gpc_order GPC GPChighlight.bg #FFFFFF #FFFFFF
highlight.comment #FF8000 #FF8000
highlight.default #0000BB #0000BB
highlight.html #000000 #000000
highlight.keyword #007700 #007700
highlight.string #DD0000 #DD0000
html_errors On On
ignore_repeated_errors Off Off
ignore_repeated_source Off Off
ignore_user_abort Off Off
implicit_flush Off Off
include_path .:/usr/local/apache/lib/php .:/usr/local/apache/lib/php
log_errors Off Off
log_errors_max_len 1024 1024
magic_quotes_gpc On On
magic_quotes_runtime Off Off
magic_quotes_sybase Off Off
max_execution_time 30 30
max_input_time -1 -1
open_basedir no value no value
output_buffering 0 0
output_handler no value no value
post_max_size 8M 8M
precision 14 14
register_argc_argv On On
register_globals Off Off
report_memleaks On On
safe_mode Off Off
safe_mode_exec_dir /usr/local/php/bin /usr/local/php/bin
safe_mode_gid Off Off
safe_mode_include_dir no value no value
sendmail_from no value no value
sendmail_path /usr/sbin/sendmail -t -i /usr/sbin/sendmail -t -i
serialize_precision 100 100
short_open_tag On On
SMTP localhost localhost
smtp_port 25 25
sql.safe_mode Off Off
track_errors Off Off
unserialize_callback_func no value no value
upload_max_filesize 2M 2M
upload_tmp_dir no value no value
user_dir no value no value
variables_order no value no value
xmlrpc_error_number 0 0
xmlrpc_errors Off Off
y2k_compliance On On

Directive Local Value Master Value
mysql.allow_persistent On On
mysql.connect_timeout 60 60
mysql.default_host no value no value
mysql.default_password no value no value
mysql.default_port no value no value
mysql.default_socket no value no value
mysql.default_user no value no value
mysql.max_links Unlimited Unlimited
mysql.max_persistent Unlimited Unlimited
mysql.trace_mode Off Off

PHP License
This program is free software; you can redistribute it and/or modify it under the terms of the PHP License as published by the PHP Group and included in the distribution in the file: LICENSE

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

If you did not receive a copy of the PHP license, or have any questions about PHP licensing, please contact license@php.net.